miniblog.

Really cute approach to reporting type errors: when there's a type error, show an example of a runtime error that the type check has prevented! Data-Driven Techniques for Type Error Diagnosis https://escholarship.org/uc/item/59s4h4pv

I'm working on arity errors in Garden, my toy programming language. Rather than just saying "expected 3, got 4 arguments", I'm trying to report where the extra argument is, or what extra argument was expected.

I'm having fun writing a simple type checker, but I'm learning firsthand why syntax-directed checking doesn't work. It prevents inference. My checker catches real bugs, but it can't handle cases like this: [1, 2].map(fun(x) { x + 1; }) I think I need bidirectional checking.